1. Field of the Invention
The present invention generally relates to image processing apparatuses and methods for processing images displayed by image display apparatuses such as television monitors and liquid crystal display panels.
2. Description of the Related Art
FIG. 1 is a block diagram of a conventional video-signal processing apparatus. A charge coupled device (CCD) sensor 1a converts a captured picture into an electrical signal. An analog-to-digital (A/D) converter 2a converts an analog video signal output from the CCD sensor 1a to a digital video signal.
An image-capturing signal processing circuit 3a generates a luminance signal based on the signal output from the CCD sensor 1a by performing color carrier elimination, aperture correction, gamma processing, etc. The image-capturing signal processing circuit 3a simultaneously generates a chroma signal by performing color interpolation, matrix transformation, gamma processing, gain adjustment, etc., and outputs video signals such as a luminous signal Y, and two chroma signals U and V. A data writing circuit 4a writes the generated video signals in a volatile random access memory (VRAM) 5a. 
The VRAM 5a is, for example, a dynamic random access memory (DRAM) provided with writing and reading ports, and performs addressing for each horizontal line.
A timing generating circuit 6a generates timing signals necessary for other circuits. A data reading circuit 7a reads video data stored in the VRAM 5a (see FIG. 4). Accordingly, the data writing circuit 4a stores data (Y0, U0; Y1, V0; Y2, U2; Y3, V2; . . . ) at sequential memory addresses for each horizontal line in the VRAM 5a, and the data reading circuit 7a reads the data for each horizontal line at address pointers H1, H2, . . . , and the data size.
A television (TV)-system signal processing circuit 8a outputs TV digital video signals by performing the signal processing (chroma encoding, band correction, composing, etc.) of the Y, U, and V signals read by the data reading circuit 7a. 
Digital-to-analog (D/A) converters 9a and 9b convert the digital video signals into analog video signals. Low-pass filters (LPFs) 10a and 10b block high-frequency noise components generated when D/A conversion is performed. A gain adjustment circuit 11a adjusts video signals from the LPF 10b to have a signal level adapted for liquid crystal display.
A liquid crystal controller 12a generates driving pulses necessary for liquid crystal display, and converts TV signals from the gain adjustment circuit 11a into signals for liquid crystal display. A liquid crystal display panel 13a displays a visible image based on signals from the liquid crystal controller 12a. 
A video amplifier 14a outputs video signals from through the LPF 10a at a TV-signal level and impedance. A television (TV) monitor 15a uses a color television broadcasting system such as the NTSC or PAL system to display images.
The operation of the above-described conventional video-signal processing apparatus is described below.
The picture signal from the CCD sensor 1a is converted into a digital video signal by the A/D converter 2a, and is processed by the signal processing circuit 3a to generate luminance signal Y, and chroma signals U and V. The Y signal is obtained by performing color carrier elimination, aperture correction, gamma conversion, etc. The U signal represents the chroma between blue and the Y signal, and the V signal represents the chroma between red and the Y signal. The U and V signals are obtained by performing color interpolation, matrix transformation, gamma conversion, etc. The Y, U, and V signals output from the signal processing circuit 3a are stored in the VRAM 5a by the data writing circuit 4a, in the order of Y0, U0; Y1, V0; Y2, U2; Y3, V2; . . . , from the top left of an image as shown in FIG. 4.
The data stored in the VRAM 5a are read in the writing order by the data reading circuit 7a, and are processed by the TV-system signal processing circuit 8a to generate separate luminance and chroma signals, composite signals, and luminance and chroma signals for the liquid crystal display panel 13a. 
The digital video signals output from the TV-system signal processing circuit 8a are converted into analog video signals by the D/A converters 9a and 9b. The analog signals are processed by the LPFs 10a and 10b so that bandwidth reduction is performed. The analog signals for the liquid crystal display panel 13a are processed by the gain adjustment circuit 11a so that level matching is performed, and is output to the liquid crystal controller 12a. At the same time, the analog signals for the TV monitor 15a are processed by the video amplifier 14a so that level matching and output impedance adjustment is performed, and are output to the TV monitor 15a. 
FIG. 2 is a block diagram of another conventional video-signal processing apparatus. Blocks identical to those in the first described conventional video-signal processing apparatus are denoted by the same reference numerals to avoid duplicate descriptions.
A DRAM 21a is used for a purpose similar to that of the VRAM 5a. The DRAM 21a stores image data to be displayed on a screen by superimposing or replacing an image captured by a CCD sensor (not shown).
A captured image reading circuit 22a reads data of images captured by the CCD sensor. A superimposing image reading circuit 23a reads the image data for superimposing stored in the DRAM 21a. 
A superimposing circuit 24a performs switching, superimposing, or replacement between the captured image data output from the captured image reading circuit 22a, and the superimposing image data output from the superimposing image reading circuit 23a. Outputs from the superimposing circuit 24a are input to a TV-system signal processing circuit 8a. 
A description of a process from the TV-system signal processing circuit 8a to a TV monitor 15a is omitted since the process is identical to that in the first described video-signal processing apparatus.
In the above-described conventional video-signal processing apparatuses, images output to the liquid crystal display 13a and the TV monitor 15a are identical. Accordingly, in the case where image capture is performed with a camera (to which the video-signal processing apparatus is applied) or the like vertically held, a subject in a picture displayed on the TV monitor 15a is horizontal (see FIG. 6D).
Accordingly, in the conventional video-signal processing apparatuses, picture rotation is performed so that picture dimensions match the dimensions of the TV monitor 15a; in other words, when a picture is rotated 90 degrees, its size must be reduced to 3/4 because the aspect ratio of the picture is 3:4.
This causes a problem when the picture is rotated and reduced in size on the liquid crystal display panel 13a, which has a smaller display area than that of the TV monitor 15a, and the subject cannot be clearly seen.
In addition, in the case where character data such as instructions for image capture are displayed on the liquid crystal display panel 13a, if characters displayed on the TV monitor 15a, and characters displayed on the liquid crystal display panel 13a have the same orientation, a problem of questionable operability occurs when the camera is vertically held because the characters on the liquid crystal display panel 13a are horizontally inclined and cannot be easily read.